GRAFFITI! This stuff has been around since some caveman etched "cave 57 SUCKS!" on a cave wall.
And as it is with most things, handling the idea of someone writing on walls is just a matter of perception and reaction.
You can perceive it to be and eyesore
or you can see it as an opportunity to experience personal expression at street level.
You can react from fear
or you can save your reaction for later as you would after a visit to any other gallery!
The choice is yours.